The American-born radical cleric Anwar al-Awlaki, a major al Qaeda figure who U.S. officials say inspired several terror plots against the U.S., was killed overnight in Yemen in a CIA drone strike, U.S. and Yemeni officials told ABC News.

A senior U.S. official told ABC News the U.S. had been tracking the high-profile jihadist for some time and had just been waiting for the perfect moment to strike. A Yemeni official said al-Awlaki was killed along with an unknown number of al Qaeda confederates.

"They were waiting for the right opportunity to get him away from any civilians," a senior administration official told ABC News.

President Obama said in an announcement today that al-Awlaki's death was a "major blow" to al Qaeda's most operational affiliate, the Yemen-based al Qaeda in the Arabian Peninsula (AQAP), and that the successful operation against him was a tribute to the intelligence community and to Yemen.

Born in New Mexico and educated in Colorado, al-Awlaki rose to prominence among extremists as a member AQAP and was a vocal preacher of jihad. His online teachings have been cited as part of the motivation behind several attacks on the U.S. homeland -- from the Fort Hood Massacre to the attempted Christmas Day bombing and the Times Square bomb plot.

In 2010, al-Awlaki was declared a "specially designated global terrorist" and became the first U.S. citizen ever to be placed on a White House-approved list for targeted killing. He nearly met his fate shortly after U.S. Navy SEALs killed al Qaeda founder Osama bin Laden in early May when a drone strike hit the convoy he was traveling but barely missed him.

Earlier this year, America's chief counter-terrorism official Michael Leiter called him and AQAP "probably the most significant risk to the U.S. homeland."

The most recent issue of an English-language al Qaeda magazine called "Inspire" prominently featured an advertisement for an upcoming message from al-Awlaki titled "Targeting the Populations of Countries That Are at War With the Muslims". The advertisement used as its background an image of Grand Central Station with U.S. security officials said in a law enforcement bulletin could have been "an allusion to the continued interest of extremists in general of targeting New York City for terrorist attacks."

Secretary of Defense Leon Panetta told reporters the U.S. was safer now that al-Awlaki had been killed.

"We had always had a tremendous concern that after getting bin Laden, someone like al-Awlaki was a primary target because of his continuing efforts to plan attacks against the United States," he said. "This has been a bad year for terrorists."